In 1443, King Sejong commissioned hangul so ordinary people could read without mastering thousands of Chinese characters. Its basic consonants depict the speech organs: ㄱ (k) shows the tongue blocking the back of the throat, ㅁ (m) a closed mouth. It's an alphabet designed like a phonetics diagram, centuries before modern phonetics existed.
In Kuşköy, a mountain village in northern Turkey, people talk across valleys by whistling Turkish. A 2015 study showed that whistled Turkish draws on both hemispheres fairly evenly, whereas spoken Turkish relies mostly on the left. The physical form of the signal, it turns out, matters to the brain.
Speech has no gaps between words. In 1996, researchers played 8-month-old babies a continuous stream of made-up syllables for just two minutes. The infants picked out the 'words' by tracking which syllables tend to follow one another. That's probability calculation, done without a calculator or any visible effort.